package org.opentrafficsim.base.geometry;
   
   import java.util.Iterator;
   import java.util.NoSuchElementException;
   
   import org.djutils.draw.line.Polygon2d;
   import org.djutils.draw.point.Point2d;
   import org.djutils.exceptions.Throw;
   
  /**
   * Shape defined by a circle.
   * <p>
   * Copyright (c) 2024-2024 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="https://opentrafficsim.org/docs/license.html">OpenTrafficSim License</a>.
   * </p>
   * @author <a href="https://github.com/wjschakel">Wouter Schakel</a>
   */
  public class CircleShape implements OtsShape
  {
  
      /** Radius. */
      private final double radius;
  
      /** Number of line segments in polygon representation. */
      private final int polygonSegments;
  
      /** Polygon representation. */
      private Polygon2d polygon;
  
      /**
       * Constructor.
       * @param radius radius.
       */
      public CircleShape(final double radius)
      {
          this(radius, DEFAULT_POLYGON_SEGMENTS);
      }
  
      /**
       * Constructor.
       * @param radius radius.
       * @param polygonSegments number of segments in polygon representation.
       */
      public CircleShape(final double radius, final int polygonSegments)
      {
          Throw.whenNull(radius, "Radius must not be null.");
          Throw.when(radius <= 0.0, IllegalArgumentException.class, "Radius must be above 0.0.");
          this.radius = radius;
          this.polygonSegments = polygonSegments;
      }
  
      @Override
      public double getMinX()
      {
          return -this.radius;
      }
  
      @Override
      public double getMaxX()
      {
          return this.radius;
      }
  
      @Override
      public double getMinY()
      {
          return -this.radius;
      }
  
      @Override
      public double getMaxY()
      {
          return this.radius;
      }
  
      @Override
      public boolean contains(final Point2d point) throws NullPointerException
      {
          return CENTER.distance(point) < this.radius;
      }
  
      @Override
      public boolean contains(final double x, final double y)
      {
          return contains(new Point2d(x, y));
      }
  
      @Override
      public double signedDistance(final Point2d point)
      {
          return CENTER.distance(point) - this.radius;
      }
  
      @Override
      public Polygon2d asPolygon()
      {
          if (this.polygon == null)
          {
              if (this.radius == 0.0)
             {
                 this.polygon = new Polygon2d(false, new Point2d(0.0, 0.0));
             }
             else
             {
                 this.polygon = new Polygon2d(new Iterator<Point2d>()
                 {
                     /** Step. */
                     private int step = 0;
 
                     @Override
                     public boolean hasNext()
                     {
                         return this.step <= CircleShape.this.polygonSegments;
                     }
 
                     @Override
                     public Point2d next()
                     {
                         Throw.when(!hasNext(), NoSuchElementException.class, "Iterator has no more elements.");
                         // at full circle (this.step == polygonSegments), make sure end point is exactly the same as the start
                         // point
                         double ang = this.step == CircleShape.this.polygonSegments ? 0.0
                                 : (2.0 * Math.PI * this.step) / CircleShape.this.polygonSegments;
                         this.step++;
                         return new Point2d(Math.cos(ang) * CircleShape.this.radius, Math.sin(ang) * CircleShape.this.radius);
                     }
                 });
             }
         }
         return this.polygon;
     }
 
     @Override
     public String toString()
     {
         return "CircleShape [radius=" + this.radius + "]";
     }
 
 }